Full-color freespace volumetric display with occlusion

ABSTRACT

A system includes a particle configured for emitting light in response to stimulation by a light beam, a first light source configured for generating a first light beam that traps the particle in a potential well created by the light beam in air, and a second light source configured for generating a second light beam that stimulates the particle to emit emission light.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a non-provisional of, and claims priority under 35U.S.C. § 119 to, U.S. Provisional Patent Application No. 62/088,066,filed Dec. 5, 2014, entitled “FULL-COLOR FREESPACE VOLUMETRIC DISPLAYWITH OCCLUSION,” the disclosure of which is incorporated herein in itentirety.

BACKGROUND

Existing three-dimensional volumetric displays can be created byionizing separate and discrete small volumes of air to create a plasma,which causes a small flash of light at the ionization locations. Thelocations at which the plasma is created can be rastered within athree-dimensional space to create a three-dimensional display. However,such displays are monochromatic and also are accompanied by a loudpopping sound because of the plasma. Furthermore, high-power, high costlasers are required to create the plasmas. Also the plasma displaysdemonstrated to date have spots that emit light in all directions(isotropically) precluding the possibility of one image point eclipsinganother to create the 3d cue of occlusion.

SUMMARY

In a first general aspect, a system includes a particle configured foremitting light in response to stimulation by a light beam, a first lightsource configured for generating a first light beam that traps theparticle in a potential well created by the light beam in air, and asecond light source configured for generating a second light beam thatstimulates the particle to emit emission light.

Implementations can include one or more of the following features, aloneor in combination with each other. For example, the emission light caninclude scattered light from the second light beam. The emission lightcan include fluorescence light emitted in response to stimulation by thesecond light beam. The emission light can include coherent laser lightemitted in response to stimulation by the second light beam. Theparticle can include a PN junction and an optical cavity configured togenerate the coherent laser light in response to the stimulation by thesecond light beam.

The particle can be an anisotropic particle that emits lightanisotropically in response to stimulation by the second light beam. Thefirst light beam can exert a force on the particle that orients theparticle in a predetermined direction in space. The potential created bythe light beam can be associated with a focal point of the first lightbeam, and the system can further include beam scanning optical elementsconfigured for translating the focal point in three-dimensional space inthe air while the particle is trapped in the potential. The beamscanning optical elements can be configured to repeatedly translate thefocal point in a pattern in the air while the particle is trapped by thefirst light beam and while the second light beam stimulates the particleto emit emission light, and wherein the pattern is repeated at a rate ofgreater than 20 Hz.

The second light beam can include visible light, and the second lightbeam can have a different color when the focal point is at differentpoints of the repeated pattern. The first light beam can includeinvisible electromagnetic radiation, and the second light beam caninclude visible electromagnetic radiation. The first light beam and thesecond light beam can propagate co-linearly.

In another general aspect, a system includes a particle configured foremitting light in response to stimulation by a light beam, a lightsource configured for generating a light beam having a first wavelength,where the light beam traps the particle in a potential well created bythe light beam in air and that stimulates the particle to emit light ofa second wavelength different from the first wavelength.

Implementations can include one or more of the following features, aloneor in combination with each other. For example, the emission light caninclude fluorescence light emitted in response to stimulation by thesecond light beam. The emission light can include coherent laser lightemitted in response to stimulation by the second light beam. Theparticle can include a PN junction and an optical cavity configured togenerate the coherent laser light in response to the stimulation by thesecond light beam. The particle can be an anisotropic particle thatemits light anisotropically in response to stimulation by the secondlight beam.

The potential created by the light beam can be associated with a focalpoint of the first light beam, and the system can further include beamscanning optical elements configured for translating the focal point inthree-dimensional space in the air while the particle is trapped in thepotential. The beam scanning optical elements can be configured torepeatedly translate the focal point in a pattern in the air while theparticle is trapped by the light beam and stimulated by the light beamto emit the light having the second wavelength, and the pattern isrepeated at a rate of greater than 20 Hz. The light beam can exert aforce on the particle that orients the particle in a predetermineddirection in space.

The details of one or more implementations are set forth in theaccompanying drawings and the description below. Other features will beapparent from the description and drawings, and from the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of a system for providing a full-color,volumetric display.

FIG. 2 is another schematic diagram of a system for providing afull-color, volumetric display.

FIG. 3 is schematic diagram of another system for providing afull-color, volumetric display.

FIG. 4 is a schematic diagram of a system in which an anisotropicparticle is trapped within the beam waist of a beam of electromagneticradiation.

FIG. 5 is a schematic diagram of a system in which anisotropic particlesare trapped within the beam waist of a beam of electromagneticradiation.

Like reference numerals in the different figures describe like elementsin the different figures.

DETAILED DESCRIPTION

While example embodiments may include various modifications andalternative forms, it should be understood, however, that there is nointent to limit example embodiments to the particular forms disclosed,but on the contrary, example embodiments are to cover all modifications,equivalents, and alternatives.

This disclosure relates to a full-color, volumetric displays that arecapable of occlusion. The display can be used, for example, as ascreenless display to present three-dimensional images and video data toa user. The three-dimensional positions of small particles can becontrolled by forces generated by one or more first lasers or lightsources, and the particles can be illuminated by one or more secondlasers or light sources to create a visible three-dimensional display.The second lasers or light sources can include lasers having differentcolors, so that the three-dimensional display can accommodate a largecolor gamut.

FIG. 1 is a schematic diagram of a system 100 for providing afull-color, volumetric display. The system includes one or more firstlight sources (e.g., lasers, light emitting diodes, etc.) 102 that canbe used to trap and manipulate the positions of one or more particles.The system 100 further includes one or more second light sources (e.g.,lasers, light emitting diodes, etc.) 104 that can be used to illuminatethe articles with a variety of different colors that may be mixed toprovide a full spectrum of visible light. In some implementations, thefirst light source(s) 102 can include a laser that operates at awavelength in the electromagnetic spectrum, which is not within therange of human vision. For example, the first light source 102 caninclude an infrared laser that provides electromagnetic radiation havinga wavelength longer than about 800 nm. The second light sources 104 caninclude a plurality of lasers (e.g., solid state lasers) that operate atdifferent wavelengths within the visible spectrum. For example, thesecond light sources 104 can include a red laser, a green laser, and ablue laser.

The electromagnetic radiation from the first light source 102 and thesecond light source 104 can be combined by an optical element (e.g., abeam splitter) 106, so that the electromagnetic radiation from the twolight sources travels co-linearly through scanning and focusing opticalelements 108. The optical elements 108 can focus the electromagneticradiation from the light sources 102, 104 to a focal point 110.

Particles can be trapped and manipulated by the light from the firstlight source 102 as a result of interactions of the particle with thelight. In some implementations, particles can be trapped at the focalpoint 110 by forces created by the focused beam(s) of light from one ormore of the light sources. In some implementations, the beam waist ofthe focused light from the first light source 102 can create a gradientforce trap, in which a strong electric field gradient attractsdielectric particles along the gradient to the region of the strongestelectric field at the center of the beam waist. Thus, a particle trappedby the gradient force trap of the light from the first light source 102can remain fixed in place in a three dimensional space. In someimplementations, particles can be trapped in potential wells very nearthe focal point 110, where the location of the minimum potential of thewells results from the combination of a gradient trapping force towardthe minimum beam waist location and a radiation pressure force in adirection of propagation of the light beam. In some implementations,particles can be trapped due to non-uniform heating of the particle bythe light. In some implementations, a beam waist having an intensityprofile that initially increases with increasing radius (e.g., a“doughnut hole” profile) may be used to trap particles, as particles maybe attracted to lower intensity regions within the beam waist.

In addition, the light beam that traps a particle can be scanned withinthe three-dimensional space, and while the light beam is scanned, thetrapped particle can be dragged through the three-dimensional space bythe forces created by the focused beam from the first light source 102.In some implementations, the light beam(s) produced by the firstsource(s) 102, 104 also may be used to orient the trapped particlewithin the three-dimensional space. For example, the light beam(s)produced by the first source(s) 102, 104 may be used to createrotational forces on the particle to turn and orient the particle at afixed location in space. The manipulation of particle orientation may beaccomplished by modifying the amplitude or polarization of the holdingbeam. For example, by tilting the lens through which the holding beampasses the light field can become skewed and asymmetric and may favor achange in particle orientation.

Light from the second light sources 104 also can be focused to the focalpoint 110. In some implementations, light from the second light sourcescan be scattered off the trapped particle, and the scattered light canbe viewed by a viewer. In some implementations, light from the secondlight sources can be absorbed by the trapped particle, which then, inresponse to the absorbed light, can emit fluorescence radiation that canbe viewed by a viewer. In such an implementation both the first andsecond sources may be invisible to the human eye, leaving only the lightemitted by the particle to be observed without being degraded by othervisible sources. Light from the second light sources 104 can includelight having a plurality of different wavelengths. For example, red,green, and blue light can be provided by the second light sources 104.

In some implementations, the trapped particle can include a PN junctionwith a light emitting band gap such as a light emitting diode or laserdiode. For example, in some implementations, the trapped particle caninclude an optical laser cavity with a partially reflecting mirror atone end of the cavity and a high-reflectivity mirror at the other end ofthe cavity. Light from the second and/or first laser beam stimulate theemission of light having a wavelength corresponding to the band gap andthe stimulated emission can be multiplied within the laser cavity, whicha portion of the light in the cavity is coupled out of the cavitythrough the partially-reflecting mirror to produce laser light. Thelaser light can be emitted in a preferential direction defined by thegeometry of the laser cavity of the particle.

In some implementations in which the trapped particle includes a PNjunction with a light emitting band gap, the first light source 102 canboth trap and manipulate the orientation of the PN junction as well asprovide pumping energy to the PN junction of the particle. Whenenergized, the particle may emit stimulated light such as laser lightthat can be visible and highly directional. The first light beam(s) fromfirst light source(s) 102 may be used to trap, pump, modulate and steerthe luminous particle's output.

The intensities of the different colors can be controlled by a computersystem 112, and by controlling the intensities of the different colors,any arbitrary color within the spectrum of human vision can be providedto the focal point 110 at which the trapped particle is held. Thefocusing and scanning optical elements 108 also can be subject tocontrol by the computer system 112, such that the focal point 110 can bemoved to different positions within the three-dimensional space asdetermined by the computer system 112.

By scanning the focal point 110 through the three-dimensional space, afull-color volumetric display can be created. For example, by rasteringthe focal point 110 through the three-dimensional space at a rapid rate(e.g., at a rate faster than the response rate of the human eye) animage of a three-dimensional object can be created in space for viewingby a viewer.

Because the position and orientation of the particle can be manipulatedin freespace, the illuminated particle may be used to draw imagesimmediately adjacent to physical objects, including observers, in theenvironment. For example, a particle trapped in the focal point of thefirst light beam can be repeatedly translated in a pattern in the airwhile the particle while the second light beam stimulates the particleto emit emission light. When the pattern is repeated at a rate that isfaster than the response of the human eye, (e.g., a at rate greater than20 Hz), the pattern may appear to be solid in space. In this manner,three-dimensional objects may appear to be created in space. Theco-location of such objects created from the interaction of light withone or more trapped particles and observers may be used to facilitatehuman interaction with an image by touch.

FIG. 2 is another schematic diagram of a system 200 for providing afull-color, volumetric display. The system includes a first light source202 that provides electromagnetic radiation that is focused by scanningand focusing optical elements 204 to a focal point 206. Light from thefirst light source 202, when focused to the focal point 206 can create agradient force trap that can trap a particle within the beam waist ofthe focused beam at the focal point 206.

The system 200 can include a plurality of second light sources 208, 212,216 and respective scanning and focusing optical elements 210, 214, 218,which, in conjunction with each other, can focus light from the secondlight sources to the focal point 206. Light from the second lightsources 210, 214, 218 can illuminate the trapped particle at the focalpoint 206, and scattered or fluorescence light from the trapped particlecan be viewed by a viewer.

A computer system 220 can control the light sources 202, 208, 212, 216(e.g., the intensities of light emitted from the light sources) and cancontrol the scanning and focusing optical elements 204, 210, 214, 218.For example, the computer system 220 can control the scanning andfocusing optical elements to move the focal point 206 within thethree-dimensional space. By scanning the focal point 206 through thethree-dimensional space, a full-color volumetric display can be created.For example, by rastering the focal point 206 through thethree-dimensional space at a rapid rate (e.g., at a rate faster than theresponse rate of the human eye) an image of a three-dimensional objectcan be created in space for viewing by a viewer.

FIG. 3 is schematic diagram of another system 300 for providing afull-color, volumetric display. The system 300 includes a light source302 that provides a light beam to scanning and focusing optical elements304. The scanning and focusing optical elements 304 can expand the beamfrom the light source 302 and provide the expanded beam to a wavefrontmodulating element 306. In some implementations, the wavefrontmodulating element 306 can include a micro-deformable mirror. In someimplementations, the wavefront modulating element 306 can include aspatial light modulator.

A plurality of individual regions 308 a, 308 b, 308 c, 308 d of thewavefront modulating element 306 can be separately and independentlycontrolled to focus light from the regions 308 a, 308 b, 308 c, 308 d toa plurality of respective focal points 310 a, 310 b, 310 c, 310 d. Eachof the plurality of focal points 310 a, 310 b, 310 c, 310 d can create agradient force trap that can trap a particle within the beam waist ofthe light at the focal point. Trapped particles can be illuminated bysecond light sources (not shown) that can illuminate the particles witha full-color spectrum of light for viewing by a viewer.

A computer system 312 can control the light sources 302 (e.g., theintensity of light emitted from the light source) and can control thescanning and focusing optical elements 304 and the wavefront modulatingelement 306. For example, a computer system 312 can control thewavefront modulating element 306 to move the focal points 310 a, 310 b,310 c, 310 d within the three-dimensional space. By scanning the focalpoints 310 a, 310 b, 310 c, 310 d through the three-dimensional space, afull-color volumetric display can be created. For example, by rasteringthe focal points 310 a, 310 b, 310 c, 310 d through thethree-dimensional space at a rapid rate (e.g., at a rate faster than theresponse rate of the human eye) and illuminating the particles with oneor more second light sources, an image of a three-dimensional object canbe created in space for viewing by a viewer.

Particles that are trapped for use in the systems 100, 200, 300described above can be isotropic or anisotropic. FIG. 4 is a schematicdiagram of a system 400 in which an anisotropic particle 402 is trappedwithin the beam waist of a beam 404 of electromagnetic radiation. Theparticle 402 is illuminated by visible light from a light source 406,and light scattered from the particle 402 can be viewed by a viewer at afirst viewing location 408. Because the particle 402 is anisotropic,light from the light source 408 may not be scattered in all directionsfrom the particle. For example, the anisotropic particle 402 may occludescattered light from reaching a viewer at a second viewing location 410.By using such anisotropic particles 402 in the systems 100, 200, 300described above, full-color volumetric displays can be created in whichthe entire display, or any particular point or points in the display,can be viewed from an independent preferential direction whilepreventing the display of the entire display, or the particular point orpoints in the display, from being viewed from another direction.Anisotropic particles might include, for example, thin wafers ofmaterials, such as silicon, which can be subdivided (e.g., by cleaving,crushing or diesawing) into small flat shapes of materials, which mightact as small mirrors that scatter light preferentially in one direction.Similarly, flat particles may be made from liquid materials, such asblack liquor, which can be spun to form a thin film and then fracturedto create small flat particles. Anisotropic particles may also be formedwith multiple facets in silicon, silicon dioxide, silicon nitride andother materials with ion milling and other techniques used to createMEMs devices. These multifacet particles may be shaped as polygonalmirrors with mirrors along one or more axes. These particles might alsoinclude complex prism structures.

FIG. 5 is a schematic diagram of a system 500 in which anisotropicparticles 502 a, 502 b, 502 c are trapped within the beam waist of abeam 504 of electromagnetic radiation. As shown in FIG. 5, the beamwaist of beam 504 has an intensity profile that has a minimum along theaxis of the beam and then increases (at least initially) with increasingradius. Particles 502 a, 502 b, 502 c can be trapped within the beam,for example, by being attracted to the minimum intensity region of thebeam waist.

The full-color volumetric displays described herein can be used in avariety of implementations. For example, the full-color volumetricdisplays can be used to display air-traffic control information, forexample, the three-dimensional positions of a number of planes near anairport, to a viewer. In another implementation, the full-colorvolumetric displays described herein can be used to provide an augmentedreality tool for engineering and construction applications. For example,three-dimensional models of mechanical, chemical, biological structurescan be displayed. In another implementation, the full-color volumetricdisplay can be provided, not within an empty space, but within a spacethat is shared with a real object, for example, to provide additionalinformation about the real object, such as internal structure of theobject or other features of the object.

Techniques described herein may be implemented by hardware, software,firmware, middleware, microcode, hardware description languages, or anycombination thereof. When implemented in software, firmware, middlewareor microcode, the program code or code segments to perform the necessarytasks may be stored in a machine or computer readable medium such as astorage medium. A processor(s) may perform the necessary tasks.

Specific structural and functional details disclosed herein are merelyrepresentative for purposes of describing example embodiments. Exampleembodiments, however, be embodied in many alternate forms and should notbe construed as limited to only the embodiments set forth herein.

It will be understood that, although the terms first, second, etc. maybe used herein to describe various elements, these elements should notbe limited by these terms. These terms are only used to distinguish oneelement from another. For example, a first element could be termed asecond element, and, similarly, a second element could be termed a firstelement, without departing from the scope of example embodiments. Asused herein, the term “and/or” includes any and all combinations of oneor more of the associated listed items.

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting of exampleembodiments. As used herein, the singular forms “a,” “an” and “the” areintended to include the plural forms as well, unless the context clearlyindicates otherwise. It will be further understood that the terms“comprises,” “comprising,” “includes” and/or “including,” when usedherein, specify the presence of stated features, integers, steps,operations, elements and/or components, but do not preclude the presenceor addition of one or more other features, integers, steps, operations,elements, components and/or groups thereof.

It should also be noted that in some alternative implementations, thefunctions/acts noted may occur out of the order noted in the figures.For example, two figures shown in succession may in fact be executedconcurrently or may sometimes be executed in the reverse order,depending upon the functionality/acts involved.

Unless otherwise defined, all terms (including technical and scientificterms) used herein have the same meaning as commonly understood by oneof ordinary skill in the art to which example embodiments belong. Itwill be further understood that terms, e.g., those defined in commonlyused dictionaries, should be interpreted as having a meaning that isconsistent with their meaning in the context of the relevant art andwill not be interpreted in an idealized or overly formal sense unlessexpressly so defined herein.

Portions of the above example embodiments and corresponding detaileddescription are presented in terms of software, or algorithms andsymbolic representations of operation on data bits within a computermemory. These descriptions and representations are the ones by whichthose of ordinary skill in the art effectively convey the substance oftheir work to others of ordinary skill in the art. An algorithm, as theterm is used here, and as it is used generally, is conceived to be aself-consistent sequence of steps leading to a desired result. The stepsare those requiring physical manipulations of physical quantities.Usually, though not necessarily, these quantities take the form ofoptical, electrical, or magnetic signals capable of being stored,transferred, combined, compared, and otherwise manipulated. It hasproven convenient at times, principally for reasons of common usage, torefer to these signals as bits, values, elements, symbols, characters,terms, numbers, or the like.

In the above illustrative embodiments, reference to acts and symbolicrepresentations of operations (e.g., in the form of flowcharts) that maybe implemented as program modules or functional processes includeroutines, programs, objects, components, data structures, etc., thatperform particular tasks or implement particular abstract data types andmay be described and/or implemented using existing hardware at existingstructural elements. Such existing hardware may include one or moreCentral Processing Units (CPUs), digital signal processors (DSPs),application-specific-integrated-circuits, field programmable gate arrays(FPGAs) computers or the like.

It should be borne in mind, however, that all of these and similar termsare to be associated with the appropriate physical quantities and aremerely convenient labels applied to these quantities. Unlessspecifically stated otherwise, or as is apparent from the discussion,terms such as “processing” or “computing” or “calculating” or“determining” of “displaying” or the like, refer to the action andprocesses of a computer system, or similar electronic computing device,that manipulates and transforms data represented as physical, electronicquantities within the computer system's registers and memories intoother data similarly represented as physical quantities within thecomputer system memories or registers or other such information storage,transmission or display devices.

Note also that the software implemented aspects of the exampleembodiments are typically encoded on some form of non-transitory programstorage medium or implemented over some type of transmission medium. Theprogram storage medium may be magnetic (e.g., a floppy disk or a harddrive) or optical (e.g., a compact disk read only memory, or “CD ROM”),and may be read only or random access. Similarly, the transmissionmedium may be twisted wire pairs, coaxial cable, optical fiber, or someother suitable transmission medium known to the art. The exampleembodiments not limited by these aspects of any given implementation.

Lastly, it should also be noted that whilst particular combinations offeatures described herein, the scope of the present disclosure is notlimited to the particular combinations, but instead extends to encompassany combination of features or embodiments herein disclosed irrespectiveof whether or not that particular combination has been specificallyenumerated.

What is claimed is:
 1. A system comprising: a particle configured foremitting light in response to stimulation by a light beam; a first lightsource configured for generating a first light beam that traps theparticle in a potential well created by the light beam in air, whereinthe potential well created by the light beam is associated with a focalpoint of the first light beam; beam scanning optical elements configuredfor translating the focal point in three-dimensional space in the airwhile the particle is trapped in the potential well; and a second lightsource configured for generating a second light beam that stimulates theparticle to emit emission light.
 2. The system of claim 1, wherein theemission light includes scattered light from the second light beam. 3.The system of claim 1, wherein the emission light includes fluorescencelight emitted in response to stimulation by the second light beam. 4.The system of claim 1, wherein the emission light includes coherentlaser light emitted in response to stimulation by the second light beam.5. The system of claim 1, wherein the particle includes a PN junctionand an optical cavity configured to generate the coherent laser light inresponse to the stimulation by the second light beam.
 6. The system ofclaim 1, wherein the particle is an anisotropic particle that emitslight anisotropically in response to stimulation by the second lightbeam.
 7. The system of claim 1, wherein the beam scanning opticalelements are configured to repeatedly translate the focal point in apattern in the air while the particle is trapped by the first light beamand while the second light beam stimulates the particle to emit emissionlight, and wherein the pattern is repeated at a rate of greater than 20Hz.
 8. The system of claim 7, wherein the second light beam includesvisible light and wherein the second light beam has a different colorwhen the focal point is at different points of the repeated pattern. 9.The system of claim 1, wherein the first light beam includes invisibleelectromagnetic radiation, and wherein the second light beam includesvisible electromagnetic radiation.
 10. The system of claim 1, whereinthe first light beam and the second light beam are co-linear.
 11. Thesystem of claim 1, wherein the first light beam exerts a force on theparticle that orients the particle in a predetermined direction inspace.
 12. A system comprising: a particle configured for emitting lightin response to stimulation by a light beam; a light source configuredfor generating the light beam, the light beam having a first wavelength,wherein the light beam is configured to trap the particle in a potentialwell created by the light beam in air, wherein the potential created bythe light beam is associated with a focal point of the light beam, andwherein the light beam is configured to stimulate the particle to emitlight of a second wavelength different from the first wavelength; andbeam scanning optical elements configured for translating the focalpoint in three-dimensional space in the air while the particle istrapped in the potential well.
 13. The system of claim 12, wherein theemission light includes fluorescence light emitted in response tostimulation by the second light beam.
 14. The system of claim 12,wherein the emission light includes coherent laser light emitted inresponse to stimulation by the second light beam.
 15. The system ofclaim 12, wherein the particle includes a PN junction and an opticalcavity configured to generate the coherent laser light in response tothe stimulation by the second light beam.
 16. The system of claim 12,wherein the particle is an anisotropic particle that emits lightanisotropically in response to stimulation by the second light beam. 17.The system of claim 12, wherein the beam scanning optical elements areconfigured to repeatedly translate the focal point in a pattern in theair while the particle is trapped by the light beam and stimulated bythe light beam to emit the light having the second wavelength, andwherein the pattern is repeated at a rate of greater than 20 Hz.
 18. Thesystem of claim 12, wherein the light beam exerts a force on theparticle that orients the particle in a predetermined direction inspace.
 19. A system comprising: a particle configured for emitting lightin response to stimulation by a light beam; a first light sourceconfigured for generating a first light beam that traps the particle ina potential well created by the light beam in air, wherein first lightbeam has an intensity profile that has a minimum along the axis of thebeam and then increases with increasing radius and wherein the potentialcreated by the light beam is associated with the axis of the light beam;beam scanning optical elements configured for translating the axis ofthe light beam in three-dimensional space in the air while the particleis trapped in the potential well; and a second light source configuredfor generating a second light beam that stimulates the particle to emitemission light.
 20. The system of claim 19, wherein the emission lightincludes scattered light from the second light beam.
 21. The system ofclaim 19, wherein the emission light includes fluorescence light emittedin response to stimulation by the second light beam.
 22. The system ofclaim 19, wherein the emission light includes coherent laser lightemitted in response to stimulation by the second light beam.
 23. Thesystem of claim 19, wherein the particle includes a PN junction and anoptical cavity configured to generate the coherent laser light inresponse to the stimulation by the second light beam.
 24. The system ofclaim 19, wherein the particle is an anisotropic particle that emitslight anisotropically in response to stimulation by the second lightbeam.
 25. The system of claim 19, wherein the first light beam includesinvisible electromagnetic radiation, and wherein the second light beamincludes visible electromagnetic radiation.
 26. The system of claim 19,wherein the first light beam and the second light beam are co-linear.27. The system of claim 19, wherein the first light beam exerts a forceon the particle that orients the particle in a predetermined directionin space.
 28. A system comprising: a particle configured for emittinglight in response to stimulation by a light beam; a light sourceconfigured for generating the light beam, the light beam having a firstwavelength, wherein the light beam is configured to trap the particle ina potential well created by the light beam in air, wherein the lightbeam has an intensity profile that has a minimum along the axis of thelight beam and then increases with increasing radius and wherein thepotential created by the light beam is associated with the axis of thelight beam, and wherein the light beam is configured to stimulate theparticle to emit light of a second wavelength different from the firstwavelength; and beam scanning optical elements configured fortranslating the axis of the light beam in three-dimensional space in theair while the particle is trapped in the potential well.
 29. The systemof claim 28, wherein the emission light includes fluorescence lightemitted in response to stimulation by the second light beam.
 30. Thesystem of claim 28, wherein the emission light includes coherent laserlight emitted in response to stimulation by the second light beam. 31.The system of claim 28, wherein the particle includes a PN junction andan optical cavity configured to generate the coherent laser light inresponse to the stimulation by the second light beam.
 32. The system ofclaim 28, wherein the particle is an anisotropic particle that emitslight anisotropically in response to stimulation by the second lightbeam.